This invention relates to; human powered devices for enhancing propulsion in, through, or upon water.
Human powered aquatic propulsion devices are often used for purposes of sport, recreation, exercise, training, rescue, and/or rehabilitation. Aquatic propulsion devices exist in different configurations, some of which rely primarily upon lower body strength and others that primarily rely upon upper body strength. Aquatic propulsion devices that rely upon upper body strength frequently utilize hand paddles as a propulsion enhancement mechanism. Examples of aquatic propulsion devices utilizing hand paddles are given in U.S. Patent Nos. 3,913,907; 3,922,740; 5,658,224; 5,288,254, and 4,913,418. Some aquatic propulsion devices utilize paddles or fins attached to a forearm, such as those described in U.S. Patent Nos. 4,521,011 and 3,786,526.
Hand paddles enhance aquatic propulsion by displacing a greater amount of water for a given movement than would result from hand movement alone. Aquatic propulsion may also be enhanced through the leveraging of force over a distance greater than that defined by a human limb movement alone. As an example, the use of oars for rowing boats leverages force over distance, thereby increasing the efficiency of human work. Unfortunately, the hand and/or forearm paddles mentioned above fail to incorporate useful leveraging action. Such hand and/or forearm paddles may be characterized as providing a water displacement distance that is the same as or less than the movement of a hand, thereby undesirably limiting the extent to which they may enhance aquatic propulsion.
A hand paddle disclosed in U.S. Patent No. 4,509,744 extends a center of displacement slightly beyond a hand, directly away from an arm. However, this invention is designed only as an exercise device to be utilized against the resistance of water. Due to design shortcomings, this and similar types of inventions would be of limited use relative to enhancing aquatic propulsion.
The torque generated by water resistance at the center of displacement and the force applied by a hand increase linearly with the distance between the center of displacement and the hand. This force must be countered by an equal but opposite force to keep a paddle substantially in plane with the hand and arm.
U.S. Patent No. 4,509,744 discloses a hand paddle that uses a wrist guide, which reduces the turning moment about a user""s wrist. Because of the proximity of the wrist to the hand relative to the distance from the hand to the center of water displacement, leveraged forces can become very great at the wrist. A wrist is typically bony and uneven on its top side, while its underside is soft, having many unprotected moving tendons. Thus, the wrist is not suitable for countering torque generated by an extended center of water displacement. The hand paddle design disclosed in U.S. Patent No. 4,509,744 is therefore problematic relative to the stresses imposed upon a user""s wrist.
A paddle may be defined as having a leading edge, which is the edge that first xe2x80x98cutsxe2x80x99 though the water on the return or non-power stroke during swimming. As the perpendicular distance of a paddle""s leading edge relative to a hand or arm increases, the paddle""s steering radius undesirably increases, and a user""s margin for error and ability to perform directional adjustments decrease. This effect is similar to using the rear wheels of a car for steering. Unfortunately, prior hand and arm paddles fail to properly position the leading edge of the paddle relative to a user""s arm or hand, thereby limiting their ease of use and effectiveness.
In addition to the aforementioned problems, the. enhanced water displacement of hand and arm paddles can be disadvantageous or dangerous when hands and arms need to be used for actions other than swimming, for example, when taking pictures, picking up objects, or adjusting, scuba or snorkeling apparatus. Removal of prior art hand and/or arm paddle assemblies can be problematic since such assemblies encumber both hands and arms.
According to one aspect of the invention, an aquatic propulsion device comprises a forearm support to be worn on a forearm of a person; an elongate member having a first end secured to the forearm support; and a paddle secured to a second end of the elongate member. A combination of the elongate member and the paddle include a grip positioned so that a person, when placing their forearm in the forearm support, may reach and hold onto the grip with a hand. The person may move the grip with the hand such that the forearm support, the elongate member and the paddle move in tandem with the hand and the forearm. A combination of the forearm support, the elongate member, the grip, and the paddle is characterized by a center of water displacement extending beyond the hand, away from the forearm.
Extending the distance between the center of water displacement and the grip directly away from the hand and forearm advantageously enhances aquatic propulsion by leveraging force over a distance or arc length greater than that defined by hand movement alone. A constraining action between the forearm support against or upon the forearm may counter a rotational moment of the paddle about the grip. The distance between the grip and the forearm support, through leveraging, significantly reduces the force required to counter the rotational moment of the paddle about the grip relative to a force that would otherwise be required proximate the hand or wrist.
Another aspect of the invention teaches that a leading edge of the paddle is substantially inline with the hand and forearm, thereby enhancing a user""s ability to perform directional adjustments. For safety and convenience, in an additional aspect of the invention, the forearm support partially encloses the forearm, such that release of the hand grip facilitates essentially free release of the aquatic propulsion device from the person.